CMake: don't add cross compile suffix to wx-config library names for iOS build

The libraries do not have this suffix. And configure also doesn't do it.

build/cmake/config.cmake

@@ -85,7 +85,7 @@ function(wx_write_config)
         set(WX_CHARTYPE ansi)
         set(lib_unicode_suffix)
     endif()
-    if(CMAKE_CROSSCOMPILING)
+    if(CMAKE_CROSSCOMPILING AND NOT IPHONE)
         set(cross_compiling yes)
         set(host_alias ${CMAKE_SYSTEM_NAME})
     else()